Ru4H4(CO)i2 and Os3H2(CO)iq are obtained in high yield and purity by reaction of H2 at atmospheric pressure at 120°in hydrocarbon solutions of Ru3(CO)i2 and Os3(CO)u, respectively. Further treatment of Os3Fl2(CO)io with H2 leads to Os4H4(CO)i2. Ru4D4(CO)i2 is obtained from Ru3(CO)i2 and D2 in hydrocarbon solvent; however, extensive hydrogen exchange with solvent is observed in the osmium system. Ru4H2D2(CO)i2 is obtained in the reaction of D2 with Ru4H2(CO)i3 and the new mixed metal complex FeRu3H4(CO)i2 is obtained from FeRu3H2(CO)i3 and H2. Substances are characterized by ir, NMR, Raman, and mass spectrometry.We report here our studies of the treatment of metal carbonyls with H2 (or D2) at atmospheric pressure and elevated temperature giving a convenient synthesis2 of a number of hydrido (or deuterio) carbonyl metal clusters. We were led to this reaction through earlier observations in the chemistry of Re4H4(CO)i2.3 This complex is readily transformed into higher carbonyls in contact with CO at atmospheric pressure as indicated in reaction sequence (1); at Re4H4(CO)P + SCO -Re3H3(CO)12 + ReH(CO)r, |h2 + |Re2(CO)10 slightly elevated temperatures, H2 evolution was observed. This suggested to us that the reverse of this transformation might be possible and indeed when H2 at atmospheric pressure is bubbled through a hydrocarbon solution of Re2(CO)io at 150°, the lower carbonyl cluster compounds are obtained, first Re3H3(CO)i2 subsequently replaced by Re4H4(CO)i2.2 We subjected a number of other carbonyls to this treatment and found several hydrido-metal carbonyl cluster complexes of ruthenium, osmium, and a mixed ironruthenium cluster can be obtained through this route. RutheniumTreatment of Ru3(CO)j2 with H2 gives Ru4H4(CO)i2 conveniently in high yield and purity. Excellent analytical data were obtained for our product which displays five maxima in the carbonyl stretching region of the ir (see Table I) consistent with that independently obtained by Piacenti and coworkers4 in an autoclave reaction of Ru3(CO)i2 with H2 at 110°and 150 atm, but in contrast to earlier reports5 of two isomers a and ß of the same formulation each with different and more complex carbonyl ir absorptions. Both we and the Italian group have shown that the spectrum reported for the "a isomer" is derived from a mixture of Ru4H4(CO)i2 and Ru3(CO)]2 which can easily be separated by column chromatography. Indeed single crystals suitable for structure determination of Ru3(CO)i26 were obtained from a solution containing "a-Ru4H4(CO)i2". Regarding the "ß isomer", we have not been able to observe any evidence for its existence either in the direct reaction of Ru3(CO),2 with H2 or in attempts to repeat the earlier

Both Ru,(CO),, and [H,Ru,(CO),,] react rapidly with cyclopentadiene in the absence of oxygen to yield [RuH(CO),(q-C,H,)],(11; M = Ru), quantitatively, characterised in part via high-yield conversion into [RuH(CO)(PPh,) (q-C5H5)]. In the presence of oxygen [{Ru(CO),(q-C5H5)},], (111; M = Ru), is obtained in ca. 70% yield. The complex [Ru(CO),(q-C,H,)],( I ; M = Ru), has been isolated and shown to be a direct precursor of (11). Treatment of ( I ; M = Ru) with [Ph,C] [BF,] gives [Ru(CO),(q-C5H5)] [BF,], while triphenylphosphine displaces C5H6 forming [Ru(CO),(PPh,),]. Carbonylation (1 00 atm) of [RuH(CO) (PPh,) (q-C5H5)] in the presence of Et,O.BF, gives [Ru(CO),(PPh,) (-q-C5H5)] [BF,] in high yield. A minor product of the reaction of Ru,(CO),, and C5H6 is tentatively identified as [ R U , H ( C O ) ~( ~~-C ~H ~) ] , (IV) ; a related fluxional osmium complex, [Os,H,(CO),(q2-C5H4)],is obtained on treating [H20s3(CO),,] with C5H6. Low-yield formation of ( I ; M = 0 s ) and (11; M = 0 s ) from reaction of Os,(CO),,, [H,Os,(CO),,],or [H,Os(CO),] with C5H6 is described.IT has been suggested 1,2 that the reaction of iron pentacarbonyl with cyclopentadiene proceeds to the observed product [{Fe(CO),(q-C,H,)},], (111; M = Fe),, via intermediate ?-C,H, and q-C,H, iron complexes, as shown in the Scheme. This is now generally accepted, following the subsequent isolation of [Fe(CO),(q-C,H,)], ( I ; M =

Pentalene, which is predicted1 to have in the ground state the polyolefin structure 1, is unstable,

Protonation of the complexes [M2(CO)(p-CO){p-C(0)C2R2)(q-C5H5)2] [M = Fe or Ru; R2 = H2, Ph, , H (Me), or H (Ph)] with H BF,*OEt, results in rapid carbon-carbon bond cleavage and formation of the p-vinyl cations [M2(CO)2(p-CO){p-C(R)=C(H)R)(q-C5H5)2] +, containing a cis arrangement of R groups. Addition of HBF,*OEt2 to [Ru,(CO) (p-CO){p-C(0)C2Me2}(q-C5H5)2] produces the cation [Ru2(CO) (p-CO)({p-C(H)(O)C,Me,)(q-C,H,),] +, which isomerises slowly to [ R u ~( C O ) ~( ~-C O ) { ~-C ( M ~) = C ( H ) M ~) ( ~-C ~H ~) ~]+. The p-vinyl cations exist in solution as isomers with cis and trans orientations of terminal ligands, shown by variable-temperature n.m.r. to interconvert ; cis isomers additionally display a fluxional oscillation of the p-vinyl ligand. Treatment of the cations with NaBH, yields p-carbene complexes [M2(CO)2(p-CO){p-C(R)CH2R)(q-C5H5)2] in good yield, also as cis and trans isomers which interconvert in solution. These result from hydride addition to the p-carbon of the p-vinyl, but addition to the or-carbon is apparent in the low-yield co-formation of the terminal ethylene complex [Ru2(C0)(p-CO),( C2H,) ( T ~-C ~H ~) ~] from the cation [Ru2(C0),(p-CO) (p-CH=CH2) (q-C5H5)2] +. Addition of sodium tetrahydroborate to [Ru,(CO)(p-CO){p-C( H)(0)C2Me2}(q-C5H5),] + provides the complex [Ru2(CO) (p-CO){p-C(Me)C(Me)CH2)(q-C5H5)2], completing a conversion of metallacyclic CO to CH2. Regeneration of the p-vinyl cation [M2(CO),(p-CO) (p-CH=CH2) ( T ~-C ~H ~) ~] + is achieved by treatment of [M2(C0),(p-CO){p-C( H) Me)(q-C5H5)2] with [CPh,] [BF,]. In Part 1 of this Series we reported the syntheses of di-iron Results and lX~u&On and diruthenium complexes [M2(CO)(p-CO)(p-C(0)C,R,>(rlp-Vinyl Cations.-Synthesis. Addition of HBF,*OEt2 to C5H5)2] (1)--(12) through reactions of alkynes with [M2(CO)4-an acetone or dichloromethane solution of the di-iron and (T)-C~H~)~].* The chemistry of these dimetallacyclopentenone diruthenium complexes [M2(CO)(p-CO){p-C(0)GR2)(q-hydrocarbon~.~*~ Aspects of this work have appeared as preliminary communications.6~' C5H&] (1)-(1 I ) results in immediate cleavage of the alkyne-CO link. The ' alkyne' portion of the dimetallacycle is protonated, generating p-vinyl cations [Mr(C0)2(p-CO)(p-CR'=C(H)R2}(q-C5H5)2][BF4] (1 3)--(23) in which R' and R2are cis to one another, while the metallacyclic ketonic carbonyl is transformed into a terminal ligand. Different behaviour is shown by the diruthenium complex (12), derived from but-2yne, which yields the appropriate p-vinyl cation (24) only very slowly and via a readily isolated intermediate ( 25). This anomaly is discussed in detail below. Infrared spectra indicated that the p-vinyl complexes are formed in clean,

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